The use of bottom-up approaches to semiconductor fabrication has grown in interest within the semiconductor industry. One such approach utilizes self-assembling block copolymers for generation of sublithographic ground rule nanometer scale patterns.
Self-assembling copolymer materials that are capable of self-organizing into nanometer-scale patterns may be applied within a recessed region of a template layer to form a nanoscale structure. Under suitable conditions, the two or more immiscible polymeric block components separate into two or more different phases on a nanometer scale, and thereby form ordered patterns of isolated nano-sized structural units. Such ordered patterns of isolated nano-sized structural units formed by the self-assembling block copolymers can be used for fabricating nano-scale structural units in semiconductor, optical, and magnetic devices. Dimensions of the structural units so formed are typically in the range of 5 to 40 nm, which are sublithographic (i.e., below the resolution of the lithographic tools).
The self-assembling block copolymers are first dissolved in a suitable solvent system to form a block copolymer solution, which is then applied onto the surface of an underlayer to form a block copolymer layer. The self-assembling block copolymers are annealed at an elevated temperature to form two sets of polymer block structures containing two different polymeric block components. The polymeric block structure may be lines or cylinders. One set of polymer block structures may be embedded in the other set of polymer block structures, or polymeric block structures belonging to different sets may alternate. The self-assembling block copolymers are non-photosensitive resists, of which the patterning is effected not by photons, i.e., optical radiation, but by self-assembly under suitable conditions such as an anneal.
While self-assembled self-aligned nanoscale structure in a hexagonal array has been known in the art, such a configuration poses geometrical limitations in placement of device components. This is particularly so since most semiconductor device arrays and nanoscale arrays are typically designed in a rectangular array, not in a hexagonal array.
In view of the above, there exists a need for a two dimensional array of self-aligned self-assembled structures in a rectangular array in which the periodicity of the structure propagates along two directions having an angle other than 60 degrees therebetween.
Particularly, there exists a need for a two dimensional rectangular array of structures having sublithographic spacing and width in two orthogonal directions.